Di-functional anionic surfactants for enhanced oil recovery

ABSTRACT

The present invention describes the synthesis and use of cleavable di-functional anionic surfactants for enhanced oil recovery applications and/or the use of sacrificial surfactants.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application for patent is a divisional application of U.S. patentapplication Ser. No. 12/874,920, filed Sep. 2, 2010, and issued on Jun.11, 2013 as U.S. Pat. No. 8,459,360, entitled “Di-Functional SurfactantsFor Enhanced Oil Recovery,” which claims the benefit of priority fromU.S. Provisional Patent Application Ser. No. 61/239,310, filed Sep. 2,2009, entitled “Di-Functional Surfactants For Enhanced Oil Recovery,”which provisional patent application is commonly assigned to theassignee of the present invention, and which disclosure is consideredpart of and is incorporated by reference in its entirety in thedisclosure of this application.

TECHNICAL FIELD

The present invention relates in general to the field of oil recovery,and more particularly, to the design and synthesis of a noveldi-functional anionic surfactant compounds for enhanced oil recovery(“EOR”) applications.

BACKGROUND INFORMATION

Without limiting the scope of the invention, its background is describedin connection with the compositions and compounds for oil recoveryapplications.

U.S. Pat. No. 5,074,358 discloses a foam for use in a subterraneanoil-bearing formation for reducing and controlling the mobility of agaseous drive fluid. According to the '358 patent, the foam is generatedusing an inert gas and a fluorocarbon surfactant solution in admixturewith an amphoteric or anionic hydrocarbon surfactant solution.

United States Patent Application No. 2008/0196893 describes a processfor the recovery of oil from subterranean reservoirs by injecting anaqueous fluid containing from about 0.05 to about 2.0% by weight of abi-functional surfactant or a mixture of surfactants containing one ormore of the following structures:

Optionally, the aqueous fluid may contain mixtures of individualsurfactants having carboxylic, and sulfonate or sulfate functionalities.The remainder of the composition includes water or brine, a cosolventand optionally a viscosity control agent, and optionally an alkali.

SUMMARY

Described herein is the synthesis of novel surfactant molecules used inEOR. Embodiments of the surfactants described are high molecular weightsulfated internal olefin sulfonate (“IOS”) sulfates and high molecularweight dialkylphenol alkoxylate sulfonate sulfates.

In general, an aspect of the invention features a method that includes amethod of treating a hydrocarbon-bearing formation which method includesselecting a composition that includes a cleavable di-functional anionicsurfactant. The di-functional anionic surfactant is sufficiently solublein water such that the di-functional anionic surfactant can be injectedinto the hydrocarbon-bearing formation. The method further includesinjecting the composition into the hydrocarbon-bearing formation. Oncein the hydrocarbon-bearing formation, the di-functional anionicsurfactant cleaves and releases a highly surface active mono-functionalsulfonate in the formation.

Implementations of the invention can include one or more of thefollowing features:

The composition can further include a sacrificial surfactant.

The sacrificial surfactant can further be hydrolyzable and may form analcohol under downhole conditions.

The hydrocarbon-bearing formation can be downhole.

The downhole conditions can include a pressure in a range from about 1bar to 1000 bars and a temperature in a range of from about 70° F. to400° F.

The method can further include fracturing the hydrocarbon formation. Thecomposition can be injected into the hydrocarbon-bearing formationduring the fracturing, after the fracturing, or both during and afterfracturing.

The hydrocarbon-bearing formation can have a wellbore therein. Themethod can further include obtaining hydrocarbons from the wellboreafter injecting the composition into the hydrocarbon-bearing formation.

The di-functional anionic surfactant can be of the formula (I):

R₁ and R₂ can be the same or different. R₁ and R₂ can each be an alkylgroup or hydrogen.R₁ and R₂ combined can include 10 to 40 carbon atoms.

R₁ and R₂ can each be an alkyl group.

The di-functional anionic surfactant can be of the formula (II):

R₁ and R₂ can be the same or different. R₁ and R₂ can each be an alkylgroup or hydrogen.R₁ and R₂ combined can include 10 to 40 carbon atoms.

R₁ and R₂ can each be an alkyl group.

The di-functional anionic surfactant can be a di-functional anionicsurfactant of the formula (I), a di-functional anionic surfactant offormula (II), or a combination thereof:

The sacrificial surfactant can be a surfactant from the group of dialkylsulfosuccinates and their alkoxylated homologues, monoalkylsulfosuccinates and their alkoxylated versions, mono alkyl succinatesand their alkoxylated versions, and alcohol alkoxysulfates. The dialkylsulfosuccinates, monoalkyl sulfosuccinates, and mono alkyl succinates ofthis group can include linear or branched C₄-C₁₆ saturated orunsaturated chains, polyethoxy or polypropoxy chains with a degree ofpolymerization ranging from 0-12, C₄-C₁₂ alkylphenol structures, orcombinations thereof. The alcohol alkoxysulfates of this group caninclude linear or branched C₆-C₃₂ chains, polyethoxy or polypropoxychains with a degree of polymerization ranging from 0-50, C₄-C₁₂alkylphenol structures, or combinations thereof.

The composition can be cleavable at reservoir pH, temperature, pressure,or a combination thereof.

The composition can be cleavable by the introduction of a catalyst intothe formation.

The composition can include a high molecular weight sulfated internalolefin sulfonate.

The composition can include a high molecular weight Dialkylphenolalkoxylate sulfonate sulfate.

In general, another aspect of the invention features a method oftreating a hydrocarbon-bearing formation that includes selecting acomposition that includes a cleavable di-functional anionic surfactantand a sacrificial surfactant. The combination of the di-functionalanionic surfactant and the sacrificial surfactant is sufficientlysoluble in water such that combination can be injected into thehydrocarbon-bearing formation. The method further includes injecting thecomposition into the hydrocarbon-bearing formation. The di-functionalanionic surfactant cleaves and releases a highly surface activemono-functional sulfonate in the formation.

Implementations of the invention can include one or more of thefollowing features:

The sacrificial surfactant can be hydrolyzable and form an alcohol underdownhole conditions.

In general, another aspect of the invention features a method oftreating a hydrocarbon-bearing formation that includes injecting acomposition into the hydrocarbon-bearing formation. The compositionincludes a first surfactant and a sacrificial surfactant. Thesacrificial surfactant causes the first surfactant to becomesufficiently soluble in water to be injected into thehydrocarbon-hearing formation.

Implementations of the invention can include one or more of thefollowing features:

The sacrificial surfactant can be hydrolyzable and may form an alcoholunder downhole conditions.

The sacrificial surfactants can be a surfactant from the group ofdialkyl sulfosuccinates and their alkoxylated homologues, mono alkylsulfosuccinates and their alkoxylated versions, mono alkyl succinates,mono alkyl maleates and their alkoxylated versions, and alcoholalkoxysulfates.

In general, another aspect of the invention features a method ofsynthesizing a di-functional anionic surfactant of formula (I).

The method includes the steps of deriving an acid treated intermediatecyclic sultone using a process that includes sulfonating a solution ofan internal olefin. The internal olefin has a general formulaR₁—C₄H₆—R₂. R₁ and R₂ can be the same or different. R₁ and R₂ can eachbe an alkyl group or hydrogen. R₁ and R₂ combined can include 10 to 40carbon atoms. The method further includes neutralizing and hydrolyzingthe acid treated intermediate cyclic sultone to yield the di-functionalanionic surfactant of formula (I). The method further includesrecovering the di-functional anionic surfactant of formula (I) from thereaction mixture.

R₁ and R₂ can each be an alkyl group.

Implementations of the invention can include one or more of thefollowing features:

The step of deriving the acid treated intermediate cyclic sultone caninclude sulfonating the solution of the internal olefin with sulfurtrioxide in air to derive an intermediate cyclic sultone. The step ofderiving the acid treated intermediate cyclic sultone can furtherinclude treating the intermediate cyclic sultone with an acid. The acidused for treating the intermediate cyclic sultone can be sulfuric acid.

The step of deriving the acid treated intermediate cyclic sultone caninclude sulfonating the solution of the internal olefin with a sulfatingmixture of sulfuric acid and sulfur trioxide to derive the acid treatedintermediate cyclic sultone.

In general, in another aspect, the invention features a method ofsynthesizing a di-functional anionic of formula (II).

The method includes alkoylating a dinonylphenol to yield an intermediatealkoxylate derivative. The step of alkoxylating is performed usingethylene oxide, propylene oxide, or a mixture of both. The methodfurther includes treating the intermediate alkoyxlate derivative with asulfur trioxide in air to form an intermediate sulfonated alkoxylatederivative. The method further includes neutralizing and hydrolyzing theintermediate sulfonated alkoxylate derivative with a base to yield thedi-functional anionic surfactant of formula (II). The method furtherincludes recovering the di-functional anionic surfactant of formula (II)from the reaction mixture. R₁ and R₂ can be the same or different. R₁and R₂ can each be an alkyl group or hydrogen. R₁ and R₂ combined caninclude 10 to 40 carbon atoms.

R₁ and R₂ can each be an alkyl group.

In general, another aspect of the invention features a composition fortreating a hydrocarbon-bearing formation. The composition includes acleavable di-functional anionic surfactant. The di-functional anionicsurfactant is sufficiently soluble in water such that the di-functionalanionic surfactant can be injected into a hydrocarbon-bearing formation.The di-functional anionic surfactant is operable under downholeconditions such that, upon injection into the hydrocarbon-bearingformation, the di-functional anionic surfactant is cleavable andoperably able to release a highly surface active monofunctionalsulfonate.

Implementations of the invention can include one or more of thefollowing features:

The composition can further include a sacrificial surfactant.

The di-functional anionic surfactant can be of the formula (I):

R₁ and R₂ can be the same or different. R₁ and R₂ can each be an alkylgroup or hydrogen.R₁ and R₂ combined can include 10 to 40 carbon atoms.

R₁ and R₂ can each be an alkyl group.

The di-functional anionic surfactant can be of the formula (II):

R₁ and R₂ can be the same or different. R₁ and R₂ can each be an alkylgroup or hydrogen.R₁ and R₂ combined can include 10 to 40 carbon atoms.

R₁ and R₂ can each be an alkyl group.

The composition can include a sacrificial surfactant. The cleavabledi-functional anionic surfactant can be a di-functional anionicsurfactant of formula (I), a di-functional anionic surfactant of formula(II), or a combination thereof. Formula (I) and Formula (II) are,respectively:

The sacrificial surfactant can be hydrolyzable and can form an alcoholunder downhole conditions.

The sacrificial surfactant can be from the group of dialkylsulfosuccinates and their alkoxylated homologues, monoalkylsulfosuccinates and their alkoxylated versions, mono alkyl succinatesand their alkoxylated versions, alcohol alkoxysulfates, and combinationsthereof. The dialkyl sulfosuccinates, monoalkyl sulfosuccinates, andmono alkyl succinates can further include linear or branched C₄-C₁₆saturated or unsaturated chains, polyethoxy or polypropoxy chains with adegree of polymerization ranging from 0-12, C₄-C₁₂ alkylphenolstructures or combinations thereof. The alcohol alkoxysulfates canfurther include linear or branched C₆-C₃₂ chains, polyethoxy orpolypropoxy chains with a degree of polymerization ranging from 0-50,C₄-C₁₂ alkylphenol structures, or combinations thereof.

The composition can be cleavable at reservoir pH, temperature, pressure,or a combination thereof.

The composition can be cleavable in the presence of a catalyst in theformation.

The composition can include a high molecular weight sulfated internalolefin sulfonate.

The composition can include a high molecular weight Dialkylphenolalkoxylate sulfonate sulfate.

In general, another aspect of the invention features a composition fortreating a hydrocarbon-bearing formation. The composition includes acleavable di-functional anionic surfactant and a sacrificial surfactant.The combination of the di-functional anionic surfactant and thesacrificial surfactant is sufficiently soluble in water such that thecombination can injected into a hydrocarbon-bearing formation. Thedi-functional anionic surfactant is operable under downhole conditionssuch that, upon injection into the hydrocarbon-bearing formation, thedi-functional anionic surfactant is cleavable and operably able torelease a highly surface active mono-functional sulfonate.

Implementations of the invention can include one or more of thefollowing features:

The sacrificial surfactant can be hydrolyzable and can form an alcoholunder downhole conditions.

In general, another aspect of the invention features a composition fortreating a hydrocarbon-bearing formation. The composition includes afirst surfactant and a sacrificial surfactant. The sacrificialsurfactant in the composition operatively causes the first surfactant tobecome sufficiently soluble in water to be injected into ahydrocarbon-bearing formation.

Implementations of the invention can include one or more of thefollowing features:

The sacrificial surfactant can be hydrolyzable and can form an alcoholunder downhole conditions.

The sacrificial surfactant can be selected from the group of dialkylsulfosuccinates and their alkoxylated homologues, mono alkylsulfosuccinates and their alkoxylated versions, monoalkyl succinates,monoalkyl maleates and their alkoxylated versions, and alcoholalkoxysulfates.

In general, another aspect of the invention features a di-functionalanionic surfactant of formula (I):

R₁ and R₂ can be the same or different. R₁ and R₂ can each be an alkylgroup or hydrogen.R₁ and R₂ combined can include 10 to 40 carbon atoms.

R₁ and R₂ can each be an alkyl group. R₁ and R₂ can each include 8 to 20carbon atoms.

In general, in another aspect, the invention features a di-functionalanionic surfactant of formula (II):

R₁ and R₂ can be the same or different. R₁ and R₂ can each be an alkylgroup or hydrogen.R₁ and R₂ combined can include 10 to 40 carbon atoms.

R₁ and R₂ can each be an alkyl group. R₁ and R₂ can each include 8 to 20carbon atoms.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages of thepresent invention, reference is now made to the detailed description ofthe invention along with the accompanying figures and in which:

FIG. 1 is a schematic illustration of an offshore oil platform withfacilities for injecting chemical solutions into a reservoir for thepurpose of flooding the reservoir to enhance the oil recovery accordingto embodiments of the present invention:

FIG. 2 shows the structure of alkane sulfonate-sulfate according to anembodiment of the present invention;

FIG. 3 shows the structure of the dialkylphenol alkoxylate sulfonatesulfate according to an embodiment of the present invention;

FIG. 4 is a schematic representation of a synthesis method for thealkane sulfonate sulfate surfactant; and

FIG. 5 is a schematic representation of a synthesis method for theDialkylphenol alkoxylate sulfonate sulfate surfactant.

DETAILED DESCRIPTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts thatcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention and do not delimit the scope of theinvention.

To facilitate the understanding of this invention, a number of terms aredefined below. Terms defined herein have meanings as commonly understoodby a person of ordinary skill in the areas relevant to the presentinvention. Terms such as “a,” “an,” and “the” are not intended to referto only a singular entity, but include the general class of which aspecific example may be used for illustration. The terminology herein isused to describe specific embodiments of the invention, but their usagedoes not delimit the invention, except as outlined in the claims.

Embodiments of the present invention describe a synthesis and use of ahigh molecular weight di-functional anionic surfactant composed of onehydrolytically stable functional group and another group capable ofbeing labile under controlled conditions. The stable group could be asulfonate functionality where as the to-be labile one could be a sulfatemoiety. Thus, a surfactant molecule, as such, can be an alkylsulfonate-sulfate. Embodiments of the present invention demonstrate theintermolecular sacrificial surfactant concept. Embodiments of thepresent invention use an alcohol ether sulfate (“ES”) as a solubilizingsacrificial agent with the primary surfactant which was a sulfonate.

Compositions and methods taught herein provide for novel strategies fortreating a hydrocarbon-bearing formation, in which a di-functionalsurfactant is injected into a hydrocarbon-bearing formation in need ofenhanced oil recovery, wherein the cleavable di-functional anionicsurfactant is sufficiently soluble in water to be injected into ahydrocarbon-bearing formation and upon injection into the formation iscleavable and releases a highly surface active mono-functionalsulfonated under downhole conditions.

Many surfactants used for enhanced oil recovery are not sufficientlysoluble in brine unless large quantities of co-surfactants and/orco-solvents are used. With some oils, especially those with a highermolecular weight or higher wax content and under some reservoirconditions, such as high temperature, commonly used surfactants becomeless soluble in the oil, so the hydrophobe size of the surfactant mustincrease correspondingly to provide the desired surface activity andgenerate lower interfacial tension. Consequently, the solubility problemof the surfactant becomes worse until there is no practical solutioneven using expensive solubilizer co-surfactants and/or co-solvents.Embodiments of the present invention address this issue by theincorporation of an extra hydrophilic functional group in the anionicsurfactant molecule which then assumes a di-functional structure. This,in turn, makes the surfactant sufficiently soluble in water so that itcan be injected into oil reservoirs to increase oil production. However,when it is time to interact with the reservoir oil, this extrafunctional group needs to be cleaved-off from the di-functionalsurfactant molecule thereby generating a highly surface activemono-functional sulfonate. For example, this extra functional group canbe a sulfate moiety, which needs to be cleavable as a function ofreservoir temperature and pH, and the stable functional group of thesurfactant molecule can be a sulfonate functionality. The cleavage ofthis extra hydrophilic group is important and being able to do so whendesired thus also important.

Embodiments of the present invention describe two novel key molecules todemonstrate this concept in Enhanced Oil Recovery (“EOR”). Thesurfactants are A) high molecular weight sulfated internal olefinsulfonate (“IOS”) sulfate, and B) high molecular weight dialkylphenolalkoxylate sulfonate sulfate. Both these molecules contain doublehydrophilic anions with the labile group being the sulfate moiety. It isthis sulfate group that could be “programmed” to be cleaved off lateron, according to embodiments of the present invention. The structure ofIOS sulfate and the process of making it is novel. Even though Monoalkylphenol alkoxylates sulfonate sulfates have appeared in the literature,the Dialkyl version is unknown at present. The representative structuresof the IOS and the dialkylphenol alkoxylate sulfonate are represented inFIGS. 2 and 3, respectively.

The di-functional surfactant molecules of embodiments of the presentinvention are synthesized as described below.

High molecular weight IOS sulfate: the IOS may be manufactured bysulfonation of a high molecular weight internal olefin, followed byadditional processing including neutralization. The intermediate formedduring this sulfonation is a cyclic sultone. Treating this sultone withsulfuric acid followed by neutralization results in the IOS sulfate.Alternatively, a mixture of sulfuric acid and Sulfur Trioxide can beused as the sulfonating-sulfating agent followed by neutralization toproduce IOS sulfate. FIG. 4 is a schematic representation of a synthesismethod for the IOS surfactant.

Dialkylphenol alkoxylate sulfonate sulfate: the Dialkylphenol is chosenas the hydrophobe as it is difficult to make a very long chainmonoalkylphenol. Thus, a Dialkylphenol such as dinonylphenol is firstalkoxylated with EO and/or PO to make the alkoxylate. This is thentreated with sulfur trioxide, followed by neutralization to produce theDialkylphenol alkoxylate sulfonate sulfate. FIG. 5 is a schematicrepresentation of a synthesis method for the Dialkylphenol alkoxylatesulfonate sulfate surfactant.

The following definitions of terms apply throughout the specificationand claims.

For methods of treating a hydrocarbon-bearing formation and/or awellbore, the term “treating” includes placing a chemical (e.g., afluorochemical, cationic polymer, or corrosion inhibitor) within ahydrocarbon-bearing formation using any suitable manner known in the art(e.g., pumping, injecting, pouring, releasing, displacing, spotting, orcirculating the chemical into a well, wellbore, or hydrocarbon-bearingformation).

The term “polymer” refers to a molecule having a structure thatessentially includes the multiple repetition of units derived, actuallyor conceptually, from molecules of low relative molecular mass. The term“polymer” includes “oligomer.”

The term “bonded” refers to having at least one of covalent bonding,hydrogen bonding, ionic bonding, Van der Waals interactions, piinteractions, London forces, or electrostatic interactions.

“Alkyl group” and the prefix “alk-” are inclusive of both straight chainand branched chain groups and of cyclic groups having up to 30 carbons(in some embodiments, up to 20, 15, 12, 10, 8, 7, 6, or 5 carbons)unless otherwise specified. Cyclic groups can be monocyclic orpolycyclic and, in some embodiments, have from 3 to 10 ring carbonatoms.

“Alkylene” is the divalent form of the “alkyl” groups defined above.

“Arylalkylene” refers to an “alkylene” moiety to which an aryl group isattached.

The term “aryl” as used herein includes carbocyclic aromatic rings orring systems, for example, having 1, 2, or 3 rings and optionallycontaining at least one heteroatom (e.g., O, S, or N) in the ring.Examples of aryl groups include phenyl, naphthyl, biphenyl, fluorenyl aswell as furyl, thienyl, pyridyl, quinolinyl, isoquinolinyl, indolyl,isoindolyl, triazolyl, pyrrolyl, tetrazolyl, imidazolyl, pyrazolyl,oxazolyl, and thiazolyl.

“Arylene” is the divalent form of the “aryl” groups defined above.

Referring to FIG. 1, an exemplary offshore oil platform is schematicallyillustrated and generally designated 10. Semi-submersible platform 12 iscentered over submerged hydrocarbon-hearing formation 14 located belowsea floor 16. Subsea conduit 18 extends from deck 20 of platform 12 towellhead installation 22 including blowout preventers 24. Platform 12 isshown with hoisting apparatus 26 and derrick 28 for raising and loweringpipe strings such as work string 30.

Wellbore 32 may extend through the various earth strata includinghydrocarbon-bearing formation 14. Casing 34 may be cemented withinwellbore 32 by cement 36. Work string 30 may include various toolsincluding, for example, sand control screen assembly 38 which ispositioned within wellbore 32 adjacent to hydrocarbon-bearing formation14. Also extending from platform 12 through wellbore 32 may be fluiddelivery tube 40 having fluid or gas discharge section 42 positionedadjacent to hydrocarbon-bearing formation 14, shown with production zone48 between packers 44, 46. When it is desired to treat the near-wellboreregion of hydrocarbon-bearing formation 14 adjacent to production zone48, work string 30 and fluid delivery tube 40 are lowered through casing34 until sand control screen assembly 38 and fluid discharge section 42are positioned adjacent to the near-wellbore region ofhydrocarbon-bearing formation 14 including perforations 50. Thereafter,a composition described herein is pumped down delivery tube 40 toprogressively treat the near-wellbore region of hydrocarbon-bearingformation 14.

FIG. 2 shows the structure of alkane sulfonate-sulfate according to anembodiment of the present invention. FIG. 3 shows the structure of thedialkylphenol alkoxylate sulfonate sulfate according to an embodiment ofthe present invention. FIG. 4 is a schematic representation of asynthesis method for the alkane sulfonate sulfate surfactant. FIG. 5 isa schematic representation of a synthesis method for the Dialkylphenolalkoxylate sulfonate sulfate surfactant.

Phase behavior procedures.

Phase Behavior Screening. Phase behavior experiments are used tocharacterize chemicals for EOR. There are many benefits in using aqueousand microemulsion phase behavior tests as a screening method. PhaseBehavior tests are used to determine and observe among other importantcharacteristics: (1) the effect of electrolytes; (2) oil and watersolubilization; (3) 1FT reduction; (4) presence or absence of gels,liquid crystals, macroemulsions and other undesirable phases; (5)microemulsion and macroemulsion viscosities; (6) macroemulsioncoalescence times; (7) identify optimalsurfactant-cosurfactant-cosolvent-alkali-polymer formulations; and/or(7) identify optimal formulations for core flood and reservoirexperiments.

A thermodynamically stable phase called a microemulsion can form withoil, water, and surfactant mixtures. Surfactants form micellarstructures in aqueous solutions at concentrations above the criticalmicelle concentration (“CMC”). When oil is added to the aqueous solutionand mixed with it to form an emulsion, the emulsion sometimes coalescesinto a separate phase at the oil-water interfaces and is referred to asa microemulsion. A microemulsion is a stable surfactant-rich distinctphase consisting of surfactant, oil, and water and possibly co-solventsand other components. This phase is thermodynamically stable in thesense that it will return to the same phase volume and composition at agiven temperature. Some workers in the past have added additionalrequirements, but for the purposes of this engineering study, the onlyrequirement will be that the microemulsion is a thermodynamically stablephase.

The phase transition is examined by keeping all variables fixed exceptfor the scanning variable. The scan variable is changed over a series ofpipettes and may include, but is not limited to, salinity, temperature,chemical (surfactant, alcohol, electrolyte, alkali, polymer), oil, whichis sometimes characterized by its equivalent alkane carbon number(“EACN”), and surfactant structure, which is sometimes characterized byits hydrophilic-lipophilic balance (“HLB”). The phase transition wasfirst characterized by Winsor (1954) into three regions: Type 1—excessoleic phase. Type III—aqueous, microemulsion and oleic phases, and theType II—excess aqueous phase. The phase transition boundaries and somecommon terminology are described as follows: Type I to III—lowercritical salinity, Type III to II—upper critical salinity, oilsolubilization ratio (Vo/Vs), water solubilization ratio (Vw/Vs), thesolubilization value where the oil and water solubilization ratios areequal is called the Optimum Solubilization Ratio (σ*), and theelectrolyte concentration where the optimum solubilization ratio occursis referred to as the Optimal Salinity (S*).

Determining Interfacial Tension: Efficient use of time and lab resourcescan lead to valuable results when conducting phase behavior scans. Acorrelation between oil and water solubilization ratios and interfacialtension was suggested by Healy and Reed (1976) and a theoreticalrelationship was later derived by Chun Huh (1979). Lowest oil-water 1FToccurs at optimum solubilization ratio as shown by the Chun Huh theory.This is equated to an interfacial tension through the Chun Huh equation,where 1FT varies with the inverse square of the solubilization ratio:

$\gamma = \frac{C}{\sigma^{2}}$

For most crude oils and microemulsions, C=0.3 is a good approximation.Therefore, a quick and convenient way to estimate 1FT is to measurephase behavior and use the Chun Huh equation to calculate 1FT. The 1FTbetween microemulsions and water and/or oil can be very difficult andtime consuming to measure and is subject to larger errors, so using thephase behavior approach to screen hundreds of combinations ofsurfactants, co-surfactants, co-solvents, electrolytes, oil, and soforth is not only simpler and faster, but avoids the measurementproblems and errors associated with measuring 1FT, especially ofcombinations that show complex behavior (gels and so forth) and will bescreened out anyway. Once a good formulation has been identified, thenit is still a good idea to measure 1FT.

Equipment: Phase behavior experiments may be created with the followingmaterials and equipment.

Mass Balance: Mass balances are used to measure chemicals for mixturesand determine initial saturation values of cores.

Water Deionizer: Deionized (“DI”) water may be prepared for use with allthe experimental solutions using a Nanopure™ filter system. This filteruses a recirculation pump and monitors the water resistivity to indicatewhen the ions have been removed. Water is passed through a 0.45 micronfilter to eliminate undesired particles and microorganisms prior to use.

Borosilicate Pipettes: Standard 5 mL borosilicate pipettes with 0.1 mLmarkings may be used to create phase behavior scans as well as rundilution experiments with aqueous solutions. Ends may be sealed using apropane and oxygen flame.

Pipette Repeater: An Eppendorf Repeater Plus® instrument may be used formost of the pipetting. This is a handheld dispenser calibrated todeliver between 25 microliter and 1 ml increments. Disposable tips maybe used to avoid contamination between stocks and allow for ease ofoperation and consistency.

Propane-oxygen Torch: A mixture of propane and oxygen gas may bedirected through a Bernz-O-Matic flame nozzle to create a hot flameabout ½ inch long. This torch may be used to flame-seal the glasspipettes used in phase behavior experiments.

Convection Ovens: Several convection ovens may be used to incubate thephase behaviors and core flood experiments at the reservoirtemperatures. The phase behavior pipettes may be primarily kept in BlueM and Memmert ovens that are monitored with mercury thermometer and oventemperature gauges to ensure temperature fluctuations are kept at aminimal between recordings. A large custom built flow oven may be usedto house most of the core flood experiments and enable fluid injectionand collection to be done at reservoir temperature.

pH Meter: An ORION research model 701/digital ionalyzer with a pHelectrode may be used to measure the pH of most aqueous samples toobtain more accurate readings. This is calibrated with 4.0, 7.0, and10.0 pH solutions. For rough measurements of pH, indicator papers may beused with several drops of the sampled fluid.

Phase Behavior Calculations: The oil and water solubilization ratios maybe calculated from interface measurements taken from phase behaviorpipettes. These interfaces may be recorded over time as the mixturesapproach equilibrium and the volume of any macroemulsions that initiallyformed decrease or disappear. The procedure for creating phase behaviorexperiments is discussed hereinafter.

Oil Solubilization Ratio” The oil solubilization ratio is defined as thevolume of oil divided by the volume of surfactant in the microemulsion.All the surfactant is presumed to be in the microemulsion phase. The oilsolubilization ratio is applied for Winsor type I and type III behavior.The volume of oil solubilized is found by reading the change betweeninitial aqueous level and excess oil (top) interface level. The oilsolubilization ratio is calculated as follows:

$\begin{matrix}{\sigma_{o} = \frac{V_{o}}{V_{s}}} & (4.1)\end{matrix}$

σ_(o)=oil solubilization ratioV_(o)=volume of oil solubilizedV_(s)=volume of surfactant

Water Solubilization Ratio: The water solubilization ratio is defined asthe volume of water divided by the volume of surfactant inmicroemulsion. All the surfactant is presumed to be in the microemulsionphase. The water solubilization ratio is applied for Winsor type III andtype II behavior. The volume of water solubilized is found by readingthe change between initial aqueous level and excess water (bottom)interface level. The water solubilization ratio is calculated asfollows:

$\begin{matrix}{\sigma_{w} = \frac{V_{w}}{V_{s}}} & (4.2)\end{matrix}$

σ_(w)=water solubilization ratioV_(w)=volume of water solubilized

Optimum Solubilization Ratio: The optimum solubilization ratio occurswhere the oil and water solubilization ratios are equal. The nature ofphase behavior screening often does not include a data point at optimum,so the solubilization ratio curves are drawn for the oil and watersolubilization ratios and the intersection of these two curves isdefined as the optimum. The following is true for the optimumsolubilization ratio:

σ_(o)=σ_(w)=σ*

σ*=optimum solubilization ratio

Phase Behavior Methodology: Methods for creating, measuring, andrecording observations are described. Scans are made using a variety ofelectrolyte mixtures described below. Oil is added to most aqueoussurfactant solutions to see if a microemulsion formed, how long it tookto form and equilibrate if it does form, what type of microemulsionformed and some of its properties such as viscosity. However, thebehavior of aqueous mixtures without oil added is also important and isalso done to determine if the aqueous solution is clear and stable overtime as desired, or becomes cloudy or separated into more than one phaseover time.

Preparation of samples: Phase behavior samples are made by firstpreparing surfactant stock solutions and combining them with brine stocksolutions in order to observe the behavior of the mixtures over a rangeof salinities. All the experiments are created at or above 0.1 wt %active surfactant concentration, which is above the typical CMC of thesurfactant.

Solution Preparation: Surfactant stocks are based on activeweight-percent surfactant (and co-surfactant when incorporated). Themasses of surfactant, co-surfactant, co-solvent, and de-ionized water(DI) are measured out on a balance and mixed in glass jars usingmagnetic stir bars. The order of addition is recorded on a mixing sheetalong with actual masses added and the pH of the final solution. Brinesolutions are created at the necessary weight percent concentrations formaking the scans.

Surfactant Stock: The chemicals being tested are first mixed in aconcentrated stock solution that usually consisted of a primarysurfactant, co-solvent and/or co-surfactant along with de-ionized water.The quantity of chemical added is calculated based on activity andmeasured by weight percent of total solution. Initial experiments are atabout 1-3% active surfactant so that the volume of the middlemicroemulsion phase would be large enough for accurate measurementsassuming a solubilization ratio of at least 10 at optimum salinity.

Polymer Stock: Often these stocks were quite viscous and made pipettingdifficult so they are diluted with de-ionized water accordingly toimprove ease of handling. Mixtures with polymer are made only for thosesurfactant formulations that showed good behavior and merited additionalstudy for possible testing in core floods. Consequently, scans includingpolymer are limited since they are done only as a final evaluation ofcompatibility with the surfactant.

Pipetting Procedure: Phase behavior components are added volumetricallyinto 5 ml pipettes using an Eppendorf Repeater Plus or similar pipettinginstrument. Surfactant and brine stocks are mixed with DI water intolabeled pipettes and brought to temperature before agitation. Almost allof the phase behavior experiments are initially created with a water oilratio (“WOR”) of 1:1, which involved mixing 2 ml of the aqueous phasewith 2 ml of the evaluated crude oil or hydrocarbon, and different WORexperiments are mixed accordingly. The typical phase behavior scanconsisted of 10-20 pipettes, each pipette being recognized as a datapoint in the series.

Order of Addition: Consideration had to be given to the addition of thecomponents since the concentrations are often several fold greater thanthe final concentration. Therefore, an order is established to preventany adverse effects resulting from surfactant or polymer coming intodirect contact with the concentrated electrolytes. The desired samplecompositions are made by combining the stocks in the following order:(1) Electrolyte stock(s); (2) Deionized water, (3) Surfactant stock; (4)Polymer stock; and (5) Crude oil or hydrocarbon. Any air bubbles trappedin the bottom of the pipettes are tapped out (prior to the addition ofsurfactant to avoid bubbles from forming).

Initial Observations: Once the components are added to the pipettes,sufficient time is allotted to allow all the fluid to drain down thesides. Then aqueous fluid levels are recorded before the addition ofoil. These measurements are marked on record sheets. Levels andinterfaces are recorded on these documents with comments over severaldays and additional sheets are printed as necessary.

Sealing and Mixing: The pipettes are blanketed with argon gas to preventthe ignition of any volatile gas present by the flame sealing procedure.The tubes are then sealed with the propane-oxygen torch to prevent lossof additional volatiles when placed in the oven. Pipettes are arrangedon the racks to coincide with the change in the scan variable. Once thephase behavior scan is given sufficient time to reach reservoirtemperature (approximately 15-30 minutes), the pipettes are invertedseveral times to provide adequate mixing. Tubes are observed for lowtension upon mixing by looking at droplet size and how uniform themixture appeared. Then the solutions are allowed to equilibrate overtime and interface levels are recorded to determine equilibration timeand surfactant performance.

Measurements and Observations: Phase behavior samples are allowed toequilibrate in oven that is set to the reservoir temperature for thecrude oil being tested. The fluid levels in the pipettes are recordedperiodically and the trend in the phase behavior observed over time.Equilibrium behavior is assumed when fluid levels ceased to changewithin the margin of error for reading the samples.

Fluid Interfaces: The fluid interfaces are crucial elements of phasebehavior experiments. From them, the phase volumes are determined andthe solubilization ratios are calculated. The top and bottom interfacesare recorded as the scan transitioned from an oil-in-water microemulsion to a water-in-oil microemulsion. Initial readings are taken oneday after initial agitation and sometimes within hours of agitation ifcoalescence appeared to happen rapidly. Measurements are takenthereafter at increasing time intervals (for example, one day, fourdays, one week, two weeks, one month, and so on) until equilibrium isreached or the experiment is deemed unessential or uninteresting forcontinued observation.

If the interfaces are hard to read, a 365 nm black light is used toilluminate the microemulsion phase and to improve the contrast betweenthe microemulsion and the excess oleic phase.

FIG. 2 shows the structure of alkane sulfonate-sulfate according to anembodiment of the present invention. FIG. 3 shows the structure of thedialkylphenol alkoxylate sulfonate sulfate according to an embodiment ofthe present invention. FIG. 4 is a schematic representation of asynthesis method for the alkane sulfonate sulfate surfactant. FIG. 5 isa schematic representation of a synthesis method for the Dialkylphenolalkoxylate sulfonate sulfate surfactant.

It is contemplated that any embodiment discussed in this specificationcan be implemented with respect to any method, kit, reagent, orcomposition of the invention, and vice versa. Furthermore, compositionsof the invention can be used to thieve methods of the invention.

It will be understood that particular embodiments described herein areshown by way of illustration and not as limitations of the invention.The principal features of this invention can be employed in variousembodiments without departing from the scope of the invention.

All publications and patent applications are herein incorporated byreference to the same extent as if each individual publication or patentapplication was specifically and individually indicated to beincorporated by reference.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.” The use of the term “or” in the claims isused to mean “and/or” unless explicitly indicated to refer toalternatives only or the alternatives are mutually exclusive, althoughthe disclosure supports a definition that refers to only alternativesand “and/or.” Throughout this application, the terms “about” or“approximately” are used to indicate that a value includes the inherentvariation of error for the device, the method being employed todetermine the value, or the variation that exists among the studysubjects.

As used in this specification and claim(s), the words “comprising” (andany form of comprising, such as “comprise” and “comprises”), “having”(and any form of having, such as “have” and “has”), “including” (and anyform of including, such as “includes” and “include”), and “containing”(and any form of containing, such as “contains” and “contain”) areinclusive or open-ended and do not exclude additional, unrecitedelements or method steps.

The term “or combinations thereof” as used herein refers to allpermutations and combinations of the listed items preceding the term.For example, “A, B, C, or combinations thereof” is intended to includeat least one of: A, B, C, AB, AC, BC, or ABC, and if order is importantin a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB.Continuing with this example, expressly included are combinations thatcontain repeats of one or more item or term, such as BB, AAA, MB, BBC,AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan willunderstand that typically there is no limit on the number of items orterms in any combination, unless otherwise apparent from the context.

While the compositions and methods of this invention have been describedin terms of described embodiments, it will be apparent to those of skillin the art that variations may be applied to the compositions and/ormethods and in the steps or in the sequence of steps of the methoddescribed herein without departing from the concept, spirit, and scopeof the invention. All such similar substitutes and modificationsapparent to those skilled in the art are deemed to be within the spirit,scope, and concept of the invention as defined by the appended claims.

REFERENCES

-   U.S. Pat. No. 5,074,358: Surfactant-stabilized foams for enhanced    oil recovery.-   United States Patent Application No. 20080196893: Process for oil    recovery using mixed surfactant composition.-   Dwarkanath, et al. “Using Co-solvents to provide gradients and    improve oil recovery during chemical flooding in a light oil    reservoir” Paper SPE 113965 presented at the 2008 SPE improved oil    recovery symposium, Tulsa, Okla., 19-23 Apr., 2008.

What is claimed is:
 1. A method of synthesizing a di-functional anionicsurfactant of formula (I) comprising:

(a) deriving an acid treated intermediate cyclic sultone using a processthat comprises sulfonating a solution of an internal olefin, wherein (i)the internal olefin has a general formula R₁—C₄H₆—R₂, (ii) R₁ and R₂ arethe same or different, (iii) R₁ and R₂ are each an alkyl group orhydrogen, and (iv) R₁ and R₂ combined comprise 10 to 40 carbon atoms;(b) neutralizing and hydrolyzing the acid treated intermediate cyclicsultone to yield the di-functional anionic surfactant of formula (I);and (c) recovering the di-functional anionic surfactant of formula (I)from the reaction mixture.
 2. The method of claim 1, wherein saidderiving the acid treated intermediate cyclic sultone comprises: (i)sulfonating the solution of the internal olefin with sulfur trioxide inair to derive an intermediate cyclic sultone, and (ii) treating theintermediate cyclic sultone with an acid.
 3. The method of claim 1,wherein said deriving the acid treated intermediate cyclic sultonecomprises sulfonating the solution of the internal olefin with asulfating mixture of sulfuric acid and sulfur trioxide to derive theacid treated intermediate cyclic sultone.
 4. A method of synthesizing adi-functional anionic of formula (II), comprising:

(a) alkoylating a dinonylphenol to yield an intermediate alkoxylatederivative; wherein the step of alkoxylating is performed using ethyleneoxide, propylene oxide, or a mixture of both; (b) treating theintermediate alkoyxlate derivative with a sulfur trioxide in air to forman intermediate sulfonated alkoxylate derivative; (c) neutralizing andhydrolyzing the intermediate sulfonated alkoxylate derivative with abase to yield the di-functional anionic surfactant of formula (II); and(d) recovering the di-functional anionic surfactant of formula (II) fromthe reaction mixture, wherein (i) R₁ and R₂ are the same or different,(ii) R₁ and R₂ are each an alkyl group or hydrogen, and (iii) R₁ and R₂combined comprise 10 to 40 carbon atoms.
 5. A composition suitable fortreating a hydrocarbon-bearing formation, said composition comprising acleavable di-functional anionic surfactant, wherein (a) thedi-functional anionic surfactant is sufficiently soluble in water suchthat the di-functional anionic surfactant is suitable for injection intothe hydrocarbon-bearing formation, and (b) the di-functional anionicsurfactant is suitable for operation in the hydrocarbon-bearingformation such that the di-functional anionic surfactant is (i)cleavable, and (ii) suitable to release a highly surface activemonofunctional sulfonate in the hydrocarbon bearing formation.
 6. Thecomposition of claim 5, wherein the composition further comprises asacrificial surfactant.
 7. The composition of claim 5, wherein thedi-functional anionic surfactant is of the formula (I):

wherein (a) R₁ and R₂ are the same or different, (b) R₁ and R₂ are eachan alkyl group or a hydrogen, and (c) R₁ and R₂ combined comprise 10 to40 carbon atoms.
 8. The composition of claim 5, wherein thedi-functional anionic surfactant is of the formula (II):

wherein (a) R₁ and R₂ are the same or different, (b) R₁ and R₂ are eachan alkyl group or a hydrogen, and (c) R₁ and R₂ combined comprise 10 to40 carbon atoms.
 9. The composition of claim 5, wherein (a) thecomposition comprises a sacrificial surfactant, (b) the di-functionalanionic surfactant selected from the group consisting of a di-functionalanionic surfactant of formula (I), a di-functional anionic surfactant offormula (II), and combinations thereof, and (c) formula (I) and formula(II) are, respectively:


10. The composition of claim 9, wherein the sacrificial surfactant isselected from the group consisting of dialkyl sulfosuccinates and theiralkoxylated homologues, monoalkyl sulfosuccinates and their alkoxylatedversions, mono alkyl succinates and their alkoxylated versions, alcoholalkoxysulfates, and combinations thereof, wherein the dialkylsulfosuccinates, monoalkyl sulfosuccinates, and mono alkyl succinatescomprise linear or branched C₄-C₁₆ saturated or unsaturated chains,polyethoxy or polypropoxy chains with a degree of polymerization rangingfrom 0-12, C₄-C₁₂ alkylphenol structures or combinations thereof. 11.The composition of claim 10, wherein the alcohol alkoxysulfates compriselinear or branched C₆-C₃₂ chains, polyethoxy or polypropoxy chains witha degree of polymerization ranging from 0-50, C₄-C₁₂ alkylphenolstructures or combinations thereof.
 12. The composition of claim 5,wherein the composition comprises a high molecular weight sulfatedinternal olefin sulfonate or a high molecular weight Dialkylphenolalkoxylate sulfonate sulfate.
 13. The composition of claim 9, whereinthe sacrificial surfactant is hydrolyzable and suitable for forming analcohol under conditions in the hydrocarbon-bearing formation.
 14. Acomposition suitable for treating a hydrocarbon-bearing formationwherein the composition comprises a first surfactant and a sacrificialsurfactant, wherein the sacrificial surfactant in the composition issuitable for causing the first surfactant to become sufficiently solublein water for injection into a hydrocarbon-bearing formation.
 15. Thecomposition of claim 14, wherein the sacrificial surfactant is selectedfrom the group consisting of dialkyl sulfosuccinates and theiralkoxylated homologues, mono alkyl sulfosuccinates and their alkoxylatedversions, monoalkyl succinates, monoalkyl maleates and their alkoxylatedversions, and alcohol alkoxysulfates.